{ANIMATIONS v2.8} ~ FBX exporting only the selected action rather than all of them (for Unity)
When working under the Animation tab, select all with A  then when looking at the Action Editor, under Summary, you can see all bones that are being moved and or rotated for the selected action.

Here you need to make sure all names and bones are valid (Ie. nothing with red lines under it when you click the arrow beside the bone name). One this is complete you can open the Modeling tab and will want to select all meshes (using Shift + LMB/RMB) and use Ctrl + A and apply the scale.

Then within the Outliner, you will want to expand the armature, then Animation, then NLA Tracks, then expand each Action Stash. Then expand the Pose tab, and with selecting the bottom-most mesh you want to export, and Shift + LMB  the armature, it will select every mesh and anything within the Armature in the outliner.

Finally, go to File->Export->FBX, under Include go Selected Objects then Shift + LMB Armature, Mesh, and Other.

Under Transform, change Forward to Z Forward. Disable Add Leaf Bones under Armature, and lastly, disable Force Start/End Keying under Bake Animation (which should be checked).

With this, you can move to the desired output folder and click Export FBX.